On Aeneid 7, 37, ‘Nunc age,’ Servius observes : ‘hinc est sequentis operis initium; ante dicta enim ex superioribus pendent.’ This is obviously correct. That ll. 37 ff. are to be regarded as the prelude to the whole second part of the Aeneid follows from the contents of these lines and also from the fact that the opening words ‘nunc age … Erato’ are a quotation from the beginning of the second half of Apollonius's Argonautica (3, 1) εἰ δ᾽ ἄϒε νῦν, Ἐρατὠ. It is with this exordium, then, that ‘l’Odyssée finit, l'Iliade d'Énée commence’ (Sainte-Beuve, Étude sur Virgile, 2nd edition, 174). We might expect to see the solemn introduction to Part II coincide with the beginning of the Seventh Book. If ever a poet was sensitive to the effects of symmetry and clearly marked arrangement, it was Virgil. And yet here, at one of the most conspicuous points of the Aeneid, he allows himself a glaring asymmetry. An attempt to remove the stumbling-block by means of violent textual criticism has been made, but is now justly forgotten. The difficulty, however, has still to be faced. Instead of pretending that everything is normal when it is not, we should try to answer the question why Virgil has here avoided what seems to be the most natural arrangement.